Valves are commonly used in devices that involve the transportation of a fluid. A typical type of valve, for example used in laboratory systems of moderate sizes, is the rotary valve.
Generally, a rotary valve has a stationary body, herein called a stator, which co-operates with a rotating body, herein called a rotor.
The stator is provided with a number of inlet and outlet ports. The ports are via bores in fluid communication with a corresponding set of orifices on an inner stator face. The inner stator face is an inner surface of the stator that is in fluid tight contact with an inner rotor face of the rotor. The rotor is typically formed as a disc and the inner rotor face is pressed against the inner stator face in rotating co-operation. The inner rotor face is provided with one or more grooves which interconnect different orifices depending on the rotary position of the rotator with respect to the stator.
Rotary valves can be designed to withstand high pressures (such as pressures above 30 MPa). They can be made from a range of materials, such as stainless steel, high performance polymeric materials and ceramics.
The number of inlets/outlets as well as the design of grooves in the rotor or the stator reflects the intended use of a specific valve.
A common type of multi-purpose valve has one inlet port (typically placed in the rotary axis of the valve) and a number of outlets ports that are placed equidistantly around the inlet port. The rotor has a single, radially extending groove that has one end in the rotary centre, thereby always connecting to the inlet, while the other end connects to any one of the outlets depending on the angular position of the rotor with respect to the stator. Such a valve is useful to direct a flow from the inlet to any of the outlets—one at a time.
More complicated arrangements, tailor-made to perform one or several specific tasks, are possible. For instance, rotary valves may be used to introduce a fluid sample into the fluid path of an analytical system.
A typical example of such a valve is the INV-907 valve available from GE Healthcare. A schematic illustration of this valve is provided in FIG. 1 to 3. The valve 20 has a first inlet 1 for connection to a liquid source (such as a pump), a second inlet 2 for introduction of a sample (typically using a syringe or a dedicated sample pump), a third inlet 3 and a first outlet 4 to/from a device for temporary storage of the fluid sample such as a retaining capillary loop 22 (well known within the art), and a second outlet 5 that connects the valve to the downstream part of the analytical or preparative system e.g. an ÄKTA™ explorer system available from GE Healthcare. In addition, the valve has two waste outlets 6, 7 to allow a fluid to exit the valve directly to waste.
The orifices of the inner stator face of the INV-907 are represented by circles in FIG. 1-3, such as the circle 23 in the FIG. 2. In addition, a groove 24 is provided in the inner stator face.
In the figures, the rotor is represented by its grooves 25, 26, 27. When the rotor is rotated, the grooves change positions with respect to the inner stator face, thus enabling new flow paths through the valve.
FIG. 1 shows a “load position”, wherein a sample may be introduced via the rotor groove 25 into the capillary loop 22 for temporary storage. At the same time the pump can provide a flow through the remaining system via the rotor groove 27. In this position, the stator groove 24 forms a small cul-de-sac.
FIG. 2 shows an “inject position”, wherein the valve is now rotated 45° to allow the capillary loop 22 to form a part of the overall flow path of the system. The pump forces, via stator groove 24 and rotor grooves 27 and 25, the sample out of the capillary loop into the system for any separation, detection or other feature provided by the system. In this position, a part of the groove 27 forms a small cul-de-sac.
FIG. 3 shows a “waste position”, allowing the pump to direct fluid directly to a waste outlet via rotor groove 27.
As mentioned above, the sample may be introduced either with a syringe or a dedicated sample pump. Using a conventional injection valve, for example of the type shown, requires that the sample pump is connected to the port that alternatively should be used for the syringe, i.e. both alternatives could not be used at the same time.
Therefore the user has to re-plumb the system to alternate between these operative modes which reduce the flexibility of the system.